Conventional definitions of a battery present health state are based on evaluation of the remaining available capacity and the impedance level during DC discharge. However, the DC discharge impedance level of a battery is never fixed, because it depends on the operating condition, ambient temperature, remaining power level, and deterioration status of the battery. Furthermore, the remaining available capacity depends on charge/discharge current magnification, discharge depth, and ambient temperature.
In view of this, diagnosis of the present health state of a battery must be carried out by a dynamic, integrated evaluation process in order to interpret the present health state of the battery correctly.